Drum washing machine

ABSTRACT

A drum washing machine that uses less wash water, reduces an amount of electricity required to heat the wash water, and reduces washing time. The drum washing machine includes a water tub to contain water therein; a rotary drum provided in the water tub so that a rotating axis of the rotary drum is inclined relative to a horizontal axis at a predetermined first angle of inclination to allow an inlet opening of the rotary drum to be directed upward and forward, with a drain hole provided on the rotary drum at a position adjacent to the inlet opening, and an internal surface of the rotary drum being inclined relative to the rotating axis of the rotary drum at a predetermined second angle of inclination so as to guide the water to the drain hole, prior to discharging the water from the rotary drum to an outside of the rotary drum through the drain hole; a drive unit to drive the rotary drum; and a water circulation unit to feed the water from the water tub into the rotary drum.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Application No.2003-50656, filed on Jul. 23, 2003, in the Korean Intellectual PropertyOffice, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a drum washing machine and, moreparticularly, to a drum washing machine that uses less water, reduces anamount of electricity required to heat the water, and reduces washingtime.

2. Description of the Related Art

In a conventional drum washing machine, a cylindrical rotary drum whichis set in a drum-type water tub inside a cabinet, is rotated torepeatedly move upward laundry, seated on an internal surface of therotary drum, along with water, thus causing the laundry and water to bedropped from a top to a bottom inside the rotary drum due to gravity,and thereby washing the laundry. An example of a conventional drumwashing machine is disclosed in Japanese Patent Laid-open PublicationNo. 2001-149685. This conventional drum washing machine has a functionof heating water to enhance the washing effect.

The conventional drum washing machine includes a water tub, a rotarydrum, and a heater. The water tub contains water therein, while therotary drum having a plurality of perforations around a sidewall thereofis rotatably set in the tub. The heater is installed at a predeterminedposition under the water tub so as to heat the water to a predeterminedtemperature. When the drum washing machine is operating and both waterand detergent are fed into the water tub, the rotary drum is rotated inthe tub at a low speed. During the washing operation of the washingmachine, the heater heats the water to a predetermined temperature,thereby enhancing the washing effect of the washing machine.

However, the conventional drum washing machine may have severalproblems. That is, it is necessary to feed water into the washingmachine to a level at which the laundry inside the rotary drum is sunkin the water which is also contained in a gap between the perforatedrotary drum and the water tub. Therefore, the conventional drum washingmachine must consume an excessive amount of water. Since theconventional drum washing machines are designed so that the water is fedinto the water tub, and flows into the rotary drum through theperforations of the rotary drum until the laundry in the rotary drum issunk in the water, a large amount of water must be fed into the watertub. Consumption of the water during the operation of the washingmachine while in washing and rinsing operations is thus excessivelyincreased, leading to an increase in cost.

Since the excessive amount of water is consumed during an operation ofthe conventional drum washing machine, the washing machine requires longperiods of time for feeding or draining the water into or from the watertub. In addition, the time for which the conventional drum washingmachine washes the laundry is further increased since the water must beheated to a predetermined temperature by the heater, before the rotarydrum starts to be rotated to wash the laundry with the heated water.Furthermore, since the large amount of water must be heated to thepredetermined temperature by the heater, the conventional drum washingmachine excessively uses electricity to heat the water.

Another disadvantage in the conventional drum washing machine is that itis very difficult to produce the rotary drum, resulting in a complexproduction process of the washing machines, since the perforations mustbe formed around the sidewall of the rotary drum to allow the water toflow between the inside of the water tub and the rotary drum, and toallow the rotary drum to spin-dry the laundry during a spin-dryingoperation.

SUMMARY OF THE INVENTION

Accordingly, it is an aspect of the present invention to provide a drumwashing machine, which uses less water, and reduces an amount ofelectricity required to heat the water, and reduces washing time,without reducing the washing effect of the drum washing machine.

It is another aspect of the present invention to provide a drum washingmachine, which has a rotary drum designed to be easily produced.

Additional aspects and/or advantages of the invention will be set forthin part in the description which follows and, in part, will be obviousfrom the description, or may be learned by practice of the invention.

The foregoing and/or other aspects of the present invention are achievedby providing a drum washing machine comprising a water tub to containwater therein, and a rotary drum provided in the water tub wherein arotating axis of the rotary drum is inclined relative to a horizontalaxis at a predetermined first angle of inclination allowing an inletopening of the rotary drum to be directed upward and forward, with adrain hole provided on the rotary drum at a position adjacent to theinlet opening, and an internal surface of the rotary drum being inclinedrelative to the rotating axis of the rotary drum at a predeterminedsecond angle of inclination so as to guide the water to the drain hole,prior to discharging the water from the rotary drum to an outside of therotary drum through the drain hole, a drive unit to drive the rotarydrum, and a water circulation unit to feed the water from the water tubinto the rotary drum.

The drum washing machine may further comprise a heater provided in alower portion of the water tub so as to heat the water.

The drum washing machine may further comprise a drain unit having adrain pipe connected to the lower portion of the water tub and a drainpump mounted to an intermediate portion of the drain pipe.

The water circulation unit may comprise a control valve mounted to thedrain pipe of the drain unit at a position around an outlet of the drainpump to control a flow direction of the water flowing from the drainpump, a water circulation pipe extending from the control valve to theinlet opening of the rotary drum, and a spray nozzle mounted to anoutlet of the water circulation pipe to spray the water into the rotarydrum.

The rotary drum may comprise a rear part which is closed and coupled toa rotating shaft at a center of the rear part, a front part spaced apartfrom the rear part, with the inlet opening provided at a central portionof the front part, and the drain hole provided on an edge of the inletopening of the front part, and a sidewall part which is closed andextends between the rear part and the front part wherein an innerdiameter of the sidewall part increases along a direction from the rearpart to the front part to allow an internal surface of the sidewall partto be inclined.

The drain hole may comprise a plurality of rows of drain holes which areprovided around an edge of the front part of the rotary drum.

It is another aspect of the present invention to provide a drum washingmachine wherein the rear part and the sidewall part of the rotary drummay be closed, and the drain hole may be provided on an edge of thesidewall part adjacent to the front part.

It is another aspect of the present invention to provide a drum washingmachine wherein the sidewall part of the rotary drum may be connected tothe front part along a junction which is rounded to provide a roundedjunction surface, with the drain hole formed on the rounded junctionsurface.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages of the invention will becomeapparent and more readily appreciated from the following description ofthe embodiments taken in conjunction with the accompanying drawings ofwhich:

FIG. 1 is a sectional view of a drum washing machine according to anembodiment of the present invention, when the washing machine is in awashing operation;

FIG. 2 is a sectional view of the drum washing machine of FIG. 1, whenthe washing machine is in a spin-drying operation;

FIG. 3 is a sectional view taken along a line of III-III′ of FIG. 1;

FIG. 4 is a perspective view of a rotary drum included in the drumwashing machine of FIG. 1;

FIG. 5 is a sectional view of the rotary drum of FIG. 4; and

FIGS. 6 and 7 are sectional views of a rotary drum, with drain holesprovided on the rotary drum according to a first modification and asecond modification of the embodiment of FIG. 1, respectively.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals refer to like elementsthroughout. The embodiments are described below to explain the presentinvention by referring to the figures.

As shown in FIG. 1, a drum washing machine according to the presentinvention includes a cabinet 10, a drum-type water tub 11, and a rotarydrum 20. The drum-type water tub 11 is installed in the cabinet 10, andcontains water therein. The rotary drum 20 is rotatably set in the watertub 11.

In the cabinet 10, the water tub 11 is installed to be inclined relativeto a horizontal axis of the cabinet 10 at a predetermined first angle aof inclination, such that a front part 11 a of the water tub 11 havingan inlet opening 11 b is placed at a position higher than a rear part 11c of the water tub 11. In the same manner as the water tub 11, therotary drum 20 is installed in the water tub 11 such that a front part22 of the rotary drum 20 having an inlet opening 23 is placed at aposition higher than a rear part 21 of the rotary drum 20. That is, arotating axis A of the rotary drum 20 is inclined relative to thehorizontal axis of the cabinet 10 at the first angle α of inclination toallow the front part 22 having the inlet opening 23 to be placed at theposition higher than the rear part 21. A rotating shaft 12, which issecurely mounted to a center of the rear part 21 of the rotary drum 20,is rotatably held in a center of the rear part 11 c of the water tub 11,thus allowing the rotary drum 20 to be rotated relative to the water tub11. The water tub 11 is suspended in the cabinet 10 by a plurality ofshock absorbing suspension units (not shown) while being apart from aninternal surface of the cabinet 10.

A motor 13 that is a drive unit to rotate the rotating shaft 12 of therotary drum 20 is installed at a position outside the rear part 11 c ofthe water tub 11. The motor 13 includes a stator 13 a which is mountedto the rear part 11 c of the water tub 11, a rotor 13 b which isrotatably placed around the stator 13 a, and a rotary disc 13 c whichcouples the rotor 13 b to the stator 13 a.

The cabinet 10 has an inlet opening 14 at a front part thereof. Theinlet opening 14 of the cabinet 10 is aligned with both the inletopening 11 b of the water tub 11 and the inlet opening 23 of the rotarydrum 20, thus allowing a user to put laundry into the rotary drum 20 ortake the laundry out of the rotary drum 20 through the three alignedinlet openings 14, 23 and 11 b. A door 15 is mounted to an edge of theinlet opening 14 so as to close the opening 14. To prevent a leakage ofthe wash water from the water tub 11, a cylindrical bellows 16 extendsbetween the inlet opening 14 of the cabinet 10 and the inlet opening 11b of the water tub 11. A cylindrical guide unit 17 is placed inside thebellows 16 to allow the user, who stands outside the inlet opening 14 ofthe cabinet 10, to easily put the laundry into the rotary drum 20 ortake the laundry out of the rotary drum 20.

A detergent supply unit 18 and a water supply unit 30 are installed inthe cabinet 10 at positions above the water tub 11 to respectively feedeach of a detergent and water into the water tub 11. The detergentsupply unit 18 is placed at the front part of the cabinet to allow theuser to easily feed the detergent into the water tub 11. The watersupply unit 30 comprises a first water feed pipe 32 which extends froman external water supply pipe 31 to the detergent supply unit 18, asecond water feed pipe 33 which extends from the detergent supply unit18 to the water tub 11, and a first control valve 34 which is mounted toan intermediate portion of the first water feed pipe 32 to control aflow of the water to be fed into the water tub 11. Due to the coupledconstruction of the detergent supply unit 18 and the water supply unit30, the water passes through the detergent supply unit 18, prior toreaching the water tub 11. Therefore, the detergent contained in thedetergent supply unit 18 is fed into the water tub 11 in a statedissolved in the water.

The drum washing machine has a heater 40 that is placed in a lowerportion of the water tub 11 so as to heat the water contained in thewater tub 11. A heater holding part 41, which is a pan-shaped part, isprovided at a lower portion of a sidewall of the water tub 11 by drawingthe lower portion of the sidewall of the tub 11 downward, as shown inFIGS. 1, 2 and 3. The heater 40 is installed in the heater holding part41 in which a predetermined amount of water is collected to a level toallow the heater 40 to be submerged into the water. Since the heater 40is placed in the heater holding part 41 having a pan-shaped appearance,the rotary drum 20 is rotated without interfering with the heater 40.

The drum washing machine also has a drain unit 50 and a watercirculation unit 60. The drain unit 50 discharges the water from thewater tub 11 to an outside of the tub 11. The water circulation unit 60feeds the water, which is heated by the heater 40 in the water tub 11,into the rotary drum 20. The drain unit 50 comprises a first drain pipe51, a drain pump 52, and a second drain pipe 53. The first drain pipe 51is connected to a drain port 42 which is provided at the heater holdingpart 41 of the lower portion of the water tub 11, thus discharging thewater from the water tub 11 to the outside of the tub 11. The drain pump52 is mounted to an intermediate portion of the first drain pipe 51. Thesecond drain pipe 53 extends from an outlet of the drain pump 52. Thewater circulation unit 60 includes a second control valve 61, a watercirculation pipe 62, and a spray nozzle 63. The second control valve 61is mounted to an intermediate portion of the second drain pipe 53 thatextends from the outlet of the drain pump 52. The water circulation pipe62 extends from the second control valve 61 to the inlet opening 23 ofthe rotary drum 20. The spray nozzle 63 is mounted to an outlet of thewater circulation pipe 62. The second control valve 61 controls a flowdirection of the wash water flowing from the outlet of the drain pump 52so as to drain the discharged wash water to an outside of the cabinet 10or to guide the discharged wash water into the water circulation pipe62. A motorized three-way valve may be used as the second control valve61. The spray nozzle 63 is held by the guide unit 17 which is placedadjacent to the inlet opening 23 of the rotary drum 20, thus sprayingthe wash water into the rotary drum 20 through the inlet opening 23. Dueto the above-described coupled construction of the drain unit 50 and thewater circulation unit 60, the water which is discharged from the lowerportion of the water tub 11 may be drained to the outside of the cabinet10 or be sprayed into the rotary drum 20. That is, when the drain pump52 is operated with the second control valve 61 controlled to guide thedischarged water to the water circulation pipe 62, as shown in FIG. 1,the discharged water passes through both the first drain pipe 51 and thewater circulation pipe 62 to be sprayed into the rotary drum 20.However, when the drain pump 52 is operated with the second controlvalve 61 controlled to guide the discharged water to the second drainpipe 53, as shown in FIG. 2, the discharged water is drained to theoutside of the cabinet 10.

As shown in FIGS. 4 and 5, the rotary drum 20, which is installed in thewater tub 11 to be inclined relative to the horizontal axis of thecabinet 10 at the first angle a of inclination, comprises the front part22 having the inlet opening 23, the rear part 21 securely coupled to therotating shaft 12, and a cylindrical sidewall part 24 extending betweenthe front part 22 and the rear part 21. The rotary drum 20 is completelyclosed along a junction between the rear part 21 and the cylindricalsidewall part 24 so as to contain the water in the drum 20. An innerdiameter of the cylindrical sidewall part 24 of the rotary drum 20gradually increases along a direction from the rear part 21 to the frontpart 22, thus allowing an internal surface of the cylindrical sidewallpart 24 of the rotary drum 20 to be inclined relative to the rotatingaxis A of the rotary drum 20 at a predetermined second angle β ofinclination. A plurality of drain holes 25 are provided along an edge ofthe inlet opening 23 of the front part 22 to discharge the water fromthe rotary drum 20 to an outside of the rotary drum 20 through the drainholes 25 when the rotary drum 20 is rotated at a high speed. As shown inFIG. 3, the rotary drum 20 also has a plurality of lifters 26 around aninternal surface of the cylindrical sidewall part 24, thus repeatedlymoving the laundry upward along with the water to drop the laundry andwash water from the top to the bottom inside the rotary drum 20 due togravity, when the rotary drum 20 is rotated in the water tub 11. Toenhance the washing effect of the drum washing machine, a plurality ofagitating blades 27 are provided on an internal surface of the rear part21 of the rotary drum 20.

Since the rotary drum 20 is installed such that the rotating axis A ofthe rotary drum 20 is inclined relative to the horizontal axis of thecabinet 10 at the first angle a of inclination, a predetermined amountof water is contained in the rotary drum 20 to allow the laundry to besunk into the water. The water is fed into the rotary drum 20 to reach alevel that is not higher than a lowermost drain hole 25 of the rotarydrum 20. The first angle a of inclination of the rotating axis A of therotary drum 20 relative to the horizontal axis of the cabinet 10 may beset to approximately 15° in order to contain an appropriate amount ofwater in the rotary drum 20 and effectively wash the laundry.

As described above, the internal surface of the rotary drum 20 isinclined relative to the rotating axis A of the rotary drum 20 at thesecond angle β of inclination, and the drain holes 25 are provided alongthe edge of the inlet opening 23 of the front part 22 of the rotary drum20. As a result, the water is guided to the drain holes 25 of the rotarydrum 20 during a rotation of the rotary drum 20. That is, when therotary drum 20 is rotated at a high speed during a spin-drying operationof the washing machine, the water is squeezed out of the laundry in therotary drum 20 to move outward in a radial direction of the rotary drum20 due to a centrifugal force, and is guided to the drain holes 25provided on the front part 22 of the rotary drum 20 along the inclinedinternal surface of the cylindrical sidewall part 24, prior to beingdischarged to the outside of the rotary drum 20. To allow a smoothdischarging of the water from the rotary drum, the second angle β ofinclination of the internal surface of the rotary drum 20 relative tothe rotating axis A of the rotary drum 20 may be set at 0.5° or higher.

FIGS. 6 and 7 are sectional views of a rotary drum 20, with drain holesprovided on the rotary drum 20 according to a first modification and asecond modification of the embodiment of FIG. 1, respectively. In thefirst modification of FIG. 6, a plurality of rows of drain holes 25 aare provided on the front part 22 of the rotary drum 20 along the edgeof the inlet opening 23 and drain holes 25 b are provided around an edgeof the cylindrical sidewall part 24 adjacent to the front part 22. Dueto the drain holes 25 a and 25 b, the rotary drum 20 of FIG. 6 moreeffectively discharges the water to the outside thereof, in comparisonwith the rotary drum 20 of FIG. 4.

In the second modification of FIG. 7, the rotary drum 20 is roundedalong a junction corner 28 between the front part 22 and the cylindricalsidewall part 24, with a plurality of drain holes 25 c being formedalong the rounded junction corner 28. The rotary drum 20 of FIG. 7 maybe reduced in a water draining effect thereof, in comparison with therotary drum 20 of FIG. 6. However, the rotary drum 20 of FIG. 7 maydesirably contain a large amount of water therein, without enlarging theangle α of inclination of the rotary drum 20 relative to the horizontalaxis of the cabinet 10.

The drum washing machine having the above-mentioned construction isoperated as follows.

To execute a washing operation, the washing machine is turned on afterlaundry is put into the rotary drum 20 and a detergent is contained inthe detergent supply unit 18. When the washing machine is turned on asdescribed above, the first control valve 34 of the water supply unit 30is opened to feed water into the water tub 11. When the water is fedinto the water tub 11, the water passes through the detergent supplyunit 18 prior to reaching the water tub 11, due to the coupling of thedetergent supply unit 18 and the water supply unit 30. Therefore, thedetergent contained in the detergent supply unit 18 is fed into thewater tub 11 while being dissolved in the water. After a predeterminedamount of water is fed into the water tub 11, the supply of water intothe water tub 11 is stopped. Since both the rear part 21 and thecylindrical sidewall part 24 of the rotary drum 20 as well as thejunction between the rear part 21 and the sidewall part 24 arecompletely closed, the water is not introduced into the rotary drum 20during the supply of the water into the water tub 11, but the water iscontained in the heater holding part 41 provided at the lower portion ofthe sidewall of the water tub 11. In addition, since it is not necessaryto feed the water into the water tub 11 to a level allowing the laundryin the rotary drum 20 to be submerged into the water, as in theconventional drum washing machine, the amount of water required to washthe laundry is substantially reduced.

When the predetermined amount of water is completely fed into the watertub 11, the heater 40 is turned on to heat the water. Since the amountof water contained in the water tub 11 is reduced, in comparison to theconventional drum washing machine, as described above, it is possible toquickly heat the water within a short period, thereby shortening thewashing time and reducing an amount of electricity required to heat thewater.

After the water in the water tub 11 is completely heated by the heater40 to a predetermined temperature, the control valve 61 of the watercirculation unit 60 is operated to permit the outlet of the drain pump52 to communicate with the water circulation pipe 62. When the drainpump 52 in the above state is operated, the heated water is dischargedfrom the heater holding part 41 to pass through both the first drainpipe 51 and the water circulation pipe 62, thus being fed into therotary drum 20. In the above state, an entire part of the laundrycontained in the rotary drum 20 is uniformly wet with the water sincethe spray nozzle 63 sprays the water onto the laundry. The rotary drum20 is rotated at a low speed by the motor 13 simultaneously with thespraying of the water into the rotary drum 20, thus washing the laundry.

During the washing operation, the entire laundry contained in the rotarydrum 20 is sufficiently wet with the water that is contained in therotary drum 20 since the rotary drum 20 is installed in the cabinet 10to be inclined relative to the horizontal axis of the cabinet 10 at thefirst angle α of inclination, as shown in FIG. 1. The drum washingmachine thus smoothly and effectively executes the washing operation.When the level of the water in the rotary drum 20 exceeds the height ofa lowermost drain hole 25 of the rotary drum 20 during the washingoperation, the water overflows from the rotary drum 20 into the watertub 11 through the drain holes 25, prior to returning from the water tub11 to the rotary drum 20 by an operation of the drain pump 52. Thecirculation of the water is continued during the washing operation. Whenthe drum washing machine performs in the washing operation, most of thewater is continuously fed from the water tub 11 into the rotary drum 20,so that the water tub 11 contains only a small amount of water therein.

When the washing operation is finished, the drum washing machineexecutes a rinsing operation to repeatedly rinse and spin-dry the washedlaundry. To execute the rinsing operation, the washed laundry must beprimarily spin-dried. To spin-dry the washed laundry, the drain pump 52is operated with the second control valve 61 controlled to permit theoutlet of the drain pump 52 to communicate with the second drain pipe53, and the rotary drum 20 is rotated at a high speed, thus spin-dryingthe washed laundry. While the rotary drum 20 is rotated at a high speedto spin-dry the laundry, the water is primarily squeezed out of thelaundry in the rotary drum 20 to move radially outward to the internalsurface of the cylindrical sidewall part 24 of the rotary drum 20 due toa centrifugal force, and is secondarily guided to the drain holes 25provided on the front part 22 of the rotary drum 20, since the internalsurface of the rotary drum 20 is inclined relative to the rotating axisA of the rotary drum 20 at the second angle β of inclination, as shownin FIG. 2. The water in the rotary drum 20 is thus discharged to theoutside of the rotary drum 20 through the drain holes 25, and the waterin the water tub 11 is drained to the outside of the cabinet 10 by theoperation of the drain pump 52. After spin-drying the washed laundry,new water enters the water tub 11 by the operation of the water supplyunit 30, and is introduced into the rotary drum 20 by the operation ofthe water circulation unit 60, in the same manner as that described forthe washing operation, thus rinsing the laundry. During the rinsingoperation, the spin-drying of the laundry and the feeding of new waterinto the water tub 11 are repeated several times.

The rinsing operation is ended with a final spin-drying of the rinsedlaundry. To finally spin-dry the rinsed laundry, the drain pump 52 isoperated with the second control valve 61 controlled to permit theoutlet of the drain pump 52 to communicate with the second drain pipe53, and the rotary drum 20 is rotated at high speeds for a predeterminedperiod of time. That is, the final spin-drying of the rinsed laundry isperformed in the same manner as an intermediate spin-drying of thelaundry during the rinsing operation.

The present invention provides a drum washing machine in which a rotarydrum is installed in a cabinet to be inclined relative to a horizontalaxis of the cabinet, and both a rear part and a sidewall part of therotary drum as well as a junction between the rear part and the sidewallpart are completely closed. Water is contained in the rotary drum duringa washing operation of the drum washing machine. Therefore, the drumwashing machine uses less water to wash laundry, without reducing thewashing effect as in the conventional drum washing machines.

In addition, the drum washing machine feeds a small amount of water froma water tub into the rotary drum after heating the small amount of waterby use of a heater, thus reducing an amount of electricity required toheat the water, and reducing the washing time. Since the drum washingmachine uses less water to wash laundry, the washing machine quicklyfeeds and drains the water into and from the water tub, thus reducingthe overall washing time.

Since the drum washing machine washes the laundry by use of the lesswater as described above, the washing machine drains less water, thusreducing the amount of wastewater causing environmental pollution.

Furthermore, the rotary drum of the drum washing machine does not havespin-drying perforations on the rear part or the sidewall part thereof,therefore resulting in a simple construction thereof.

Although a few embodiments of the present invention have been shown anddescribed, it would be appreciated by those skilled in the art thatchanges may be made in these embodiments without departing from theprinciples and spirit of the invention, the scope of which is defined inthe claims and their equivalents.

1. A drum washing machine, comprising: a water tub to contain watertherein; a rotary drum included in the water tub and comprising: arotating axis of the rotary drum is inclined relative to a horizontalaxis at a predetermined first angle of inclination allowing an inletopening of the rotary drum to be directed upward and forward, a drainhole provided on the rotary drum at a position adjacent to the inletopening, and an internal surface of the rotary drum being inclinedrelative to the rotating axis of the rotary drum at a predeterminedsecond angle of inclination so as to guide the water to the drain hole,prior to discharging the water from the rotary drum to an outside of therotary drum through the drain hole; a drive unit to drive the rotarydrum; and a water circulation unit to feed the water from the water tubinto the rotary drum.
 2. The drum washing machine of claim 1, furthercomprising a heater provided in a lower portion of the water tub whichheats the water.
 3. The drum washing machine of claim 2, furthercomprising a drain unit having a drain pipe connected to the lowerportion of the water tub and a drain pump mounted to an intermediateportion of the drain pipe.
 4. The drum washing machine of claim 3,wherein the water circulation unit comprising: a control valve mountedto the drain pipe of the drain unit at a position around an outlet ofthe drain pump to control a flow direction of the water flowing from thedrain pump; a water circulation pipe extending from the control valve tothe inlet opening of the rotary drum; and a spray nozzle mounted to anoutlet of the water circulation pipe to spray the water into the rotarydrum.
 5. The drum washing machine of claim 1, further comprising a drainunit having a drain pipe connected to a lower portion of the water tuband a drain pump mounted to an intermediate portion of the drain pipe.6. The drum washing machine of claim 1, wherein the water circulationunit comprising: a control valve mounted to the drain pipe of the drainunit at a position around an outlet of the drain pump to control a flowdirection of the water flowing from the drain pump; a water circulationpipe extending from the control valve to the inlet opening of the rotarydrum; and a spray nozzle mounted to an outlet of the water circulationpipe to spray the water into the rotary drum.
 7. The drum washingmachine of claim 1, wherein the rotary drum comprising: a rear partwhich is closed and coupled to a rotating shaft at a center of the rearpart; a front part spaced apart from the rear part, with the inletopening provided at a central portion of the front part, and the drainhole provided on an edge of the inlet opening of the front part; and asidewall part which is closed and extends between the rear part and thefront part wherein an inner diameter of the sidewall part increasesalong a direction from the rear part to the front part to allow aninternal surface of the sidewall part to be inclined.
 8. The drumwashing machine of claim 7, wherein the drain hole comprising aplurality of rows of drain holes provided around an edge of the frontpart of the rotary drum.
 9. The drum washing machine of claim 1, whereinthe rotary drum comprising: a rear part which is closed and coupled to arotating shaft at a center of the rear part; a front part spaced apartfrom the rear part, with the inlet opening provided at a central portionof the front part; and a sidewall part which is closed and extendsbetween the rear part and the front part wherein an inner diameter ofthe sidewall part increases along a direction from the rear part to thefront part to allow an internal surface of the sidewall part to beinclined, the sidewall part having the drain hole which is provided onan edge of the sidewall part adjacent to the front part.
 10. The drumwashing machine of claim 1, wherein the rotary drum comprising: a rearpart, with a rotating shaft coupled to a center of the rear part; afront part spaced apart from the rear part, with the inlet openingprovided at a central portion of the front part; and a sidewall partextending between the rear part and the front part wherein an innerdiameter of the sidewall part increases along a direction from the rearpart to the front part to allow an internal surface of the sidewall partto be inclined, the sidewall part being connected to the front partalong a rounded junction surface, with the drain hole formed on therounded junction surface.
 11. A drum washing machine, comprising: awater tub to contain water therein; and a rotary drum installed in thewater tub by use of a rotating shaft and comprising: an internal surfaceof the rotary drum being inclined relative to a rotating axis of therotary drum so that an inner diameter of the rotary drum increases alonga direction from a rear part coupled to the rotating shaft to a frontpart having an inlet opening, the rotary drum being closed around asidewall part thereof, and a drain hole being provided on the rotarydrum at a position adjacent to the inlet opening.
 12. A drum washingmachine, comprising: a water tub to contain water therein; a rotary drumincluded in the water tub to be inclined so that a front part of therotary drum having an inlet opening is positioned to be higher than arear part of the rotary drum coupled to a rotating shaft and comprising:an internal surface of the rotary drum being inclined so that an innerdiameter of the rotary drum increases along a direction from the rearpart to the front part, and a drain hole provided on the rotary drum ata position adjacent to the inlet opening of the front part; a drive unitto drive the rotary drum; and a water circulation unit to feed the waterfrom the water tub into the rotary drum.
 13. The drum washing machine ofclaim 9, wherein the drain hole comprising a plurality of drain holesprovided on the edge of the sidewall part adjacent to the front part ofthe rotary drum.
 14. The drum washing machine of claim 10, wherein thedrain hole comprising a plurality of drain holes provided on the edge ofthe sidewall part adjacent to the front part of the rotary drum.
 15. Thedrum washing machine of claim 11, wherein the drain hole comprising aplurality of drain holes provided on the edge of the sidewall partadjacent to the front part of the rotary drum.
 16. The drum washingmachine of claim 12, wherein the drain hole comprising a plurality ofdrain holes provided on the edge of the sidewall part adjacent to thefront part of the rotary drum.
 17. The drum washing machine of claim 1,further comprising: a detergent supplying unit; and a water supplyingunit installed in a cabinet above the water to respectively feed each ofa detergent and water into the water tub.
 18. The drum washing machineof claim 17, wherein the detergent supply unit is placed at a front partof the cabinet to allow the user to feed the detergent into the watertub.
 19. The drum washing machine of claim 17, wherein the water supplyunit comprising: a first water feed pipe which extends from an externalwater supply pipe to the detergent supply unit; a second water feed pipewhich extends from the detergent supply unit to the water tub; and acontrol valve which is mounted to an intermediate portion of the firstwater feed pipe to control a flow of the water to be fed into the watertub.
 20. The drum washing machine of claim 2, wherein the heater isinstalled in a heater holding part in which a predetermined amount ofwater is collected to a level to allow the heater to be submerged intothe water.
 21. The drum washing machine of claim 21, wherein the heaterholding part has a pan-shaped appearance.
 22. The drum washing machineof claim 5, wherein the drain pipe comprising: a first drain pipeconnected to a drain port provided at the lower portion of the watertub; and a second drain pipe which extends from an outlet of the drainpump and allows water to be drained to an outside of a cabinet.
 23. Amethod of washing laundry in a drum washing machine, the methodcomprising: feeding water into a water tub; stopping the water suppliedinto the water tub after a predetermined amount of water is fed into thewater tub; holding the water in a heater holding part provided at alower portion of a sidewall part of the water tub prior to feeding thewater into a rotary drum; feeding the water into the rotary drum;overflowing water from the rotary drum into the water tub when a levelof the water in the rotary drum exceeds a height of a drain hole in alowermost position on the rotary drum; circulating the water from thewater tub to the rotary drum continuously so that the water tub containsa small amount of water therein; rinsing the laundry; and spin-dryingthe laundry.
 24. The method of claim 23, wherein the feeding water intothe water tub comprising supplying water to a detergent supply unitprior to the water reaching the water tub due to coupling of thedetergent supply unit and a water supply unit.
 25. The method of claim23, wherein the holding the water in the heater holding part comprisingheating the water to a predetermined temperature using a heater.
 26. Themethod of claim 23, wherein the feeding the water into the rotary drumcomprising spraying the laundry contained in the rotary drum with waterusing a spray nozzle while simultaneously rotating the rotary drum at alow speed.
 27. The method of claim 23, wherein the rinsing of thelaundry comprising: spin-drying the laundry wherein the rotary drum isrotated at a high speed and the water is spin-dried out of the laundryin the rotary drum to move radially outward to an internal surface of asidewall of the rotary drum due to a centrifugal force and issecondarily guided to a plurality of drain holes provided on a frontpart of a rotary drum and discharged to the outside of the rotary drumthrough the plurality of drain holes and drained to an outside of acabinet; and supplying new water into the water tub to rinse thelaundry.